Fuel Issues - FCA?

[Rdchan98]

Coming home last night, I noticed the truck had started missing, and fuel was knocking.

I happened to be monitoring rail pressure at the time and noticed it hit a max of 29,968psi and held there even after I let off the throttle, pulled over and shut it off, looked under the hood, and wiggled connectors on CP3 and fuel rail sensor.

Started and ran fine till I tried to take off and had bad fuel knock in 3rd gear, tried everything again a few times, it finally cleared up but did it a couple more times on the way home, I would let out and keep trying to speed up till it fixed itself.

I tried to recreate the issue today, and it never had a problem.

I did notice that rail pressure wasn’t climbing like it should when it was knocking and missing.

II 33% CP3 and 90hp DDP injectors, both with less than 1500 miles on them

The only code that ever came up was p0191

Does anyone have advice?

Failing FCA?

Failing CP3?

The code is for rail pressure sensor, would a bad pressure sensor make it fuel knock and miss?

lift pump pressure has a 5psi dummy light that never came on, so I think lift pressure is fine

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[Corkey]

https://sensorguides.com/fuel-rail-s...oubleshooting/

Scroll down a bit, and you'll see the troubleshooting symptoms.

You could verify on the sensor that the order is getting full voltage.

You should see 5 volts.

AK Bob, correct me if I'm wrong.

I'm going off memory at the moment.

II has the bag of parts as well, which includes the FCA.

Also, is your rail plugged or shimmed?

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[Rdchan98]

https://sensorguides.com/fuel-rail-s...oubleshooting/

Scroll down a bit, and you'll see the troubleshooting symptoms.

You could verify on the sensor that the order is getting full voltage.

You should see 5 volts.

AK Bob, correct me if I'm wrong.

I'm going off memory at the moment.

II has the bag of parts as well, which includes the FCA.

Also, is your rail plugged or shimmed?

The rail is plugged in.

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[Corkey]

The rail is plugged in.

The only reason I ask is if it's shimmed when the rail is over X amount of fuel, it dumps back into the tank.

The spring inside behind the shim will lose its strength and start to burp more fuel as time passes.

Generally, when the fuel rail pressure relief is activated, you'll get a DTC.

Have you unplugged the FCA off the back of the CP3, started the truck, gathered actual vs. desired on the fuel rail PID, turn off?

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[Rdchan98]

The only reason I ask is if it's shimmed when the rail is over X amount of fuel, it dumps back into the tank.

The spring inside behind the shim will lose its strength and start to burp more fuel as time passes.

Generally, when the fuel rail pressure relief is activated, you'll get a DTC.

Have you unplugged the FCA off the back of the CP3, started the truck, gathered actual vs. desired on the fuel rail PID, turn off?

I have not.

I'll try that tomorrow and probably order a pressure sensor after I find the correct part number.

The sensor is the only non-new fuel component, and I'm sure the water didn't help it, either.

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[Corkey]

I have not.

I'll try that tomorrow and probably order a pressure sensor after I find the correct part number.

The sensor is the only non-new fuel component, and I'm sure the water didn't help it, either.

Before throwing money at her, quiet yet, remove the 1 connector off the back of the CP3.

This gives 100 percent to the rail at idle.

It will sound rough and different.

Arrange the PIDs on the monitor before starting.

This won't hurt anything, but I would only gather the info and shut it off.

Do not hit the pedal during this.

You should be very close to one another for A\D.

If it all pans out well, I would get a reference for voltage on the sensor.

So far, it's 0 spent, and you are eliminating possibilities of the cause.

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[Rdchan98]

The results from unplugging the FCA seem to be doing what they should, although my issue is intermittent.

What do you all think?

I’m leaning toward a rail pressure sensor.

I’ll have to pull it in the shop to test it, so I’ll probably go ahead and have one on standby.

The fuel system was replaced due to water contamination, and the sensor wasn’t changed, so I’d feel better replacing it.

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[AK Bob]

The results from unplugging the FCA seem to be doing what they should, although my issue is intermittent.

What do you all think?

I’m leaning toward a rail pressure sensor.

I’ll have to pull it in the shop to test it, so I’ll probably go ahead and have one on standby.

The fuel system was replaced due to water contamination, and the sensor wasn’t changed, so I’d feel better replacing it.

The P0191 trouble code also points towards the fuel rail pressure sensor.

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[Rdchan98]

The P0191 trouble code also points towards the fuel rail pressure sensor.

My only concern was most pressure sensor failures I've seen.

They either work or don't, but I've never diagnosed a rail pressure sensor on a Cummins, so I suppose anything's possible.

Thanks for the help, guys.

I'm glad to have some knowledgeable people to ask.

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[AK Bob]

My only concern was most pressure sensor failures I've seen.

They either work or don't, but I've never diagnosed a rail pressure sensor on a Cummins, so I suppose anything's possible.

Thanks for the help, guys.

I'm glad to have some knowledgeable people to ask.

Yes, I hear you.

I don't know if they can just be skewed and read wrong.

See the attached information on the trouble code.

Please keep us posted, hopefully we can all learn from this.

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